Apparatus and method for recording sound on film



Nov. 3, 1936. s. c. WHITMAN APPARATUS AND METHOD FOR RECORDING SOUND ON FILMS Filed Dec. 6;"1932 I V 7% Y\ IIYKENTOR. iVfiLt/rzam Stewart 6*.

BY W ATTORNEYS.

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Patented Nov. 3, 1936 UNITED STATES PATENT OFFICE APPARATUS AND METHOD FOR nncoanma SOUND ON FILM Stewart 0. Whitman, New York, N. Y.

Application December 6, 1932, Serial No. 645,996

13 Claims.

An object of this invention is to produce a photographic sound-on-film recording device which is free from frequency limitations.

Another object of this invention is to provide a recording device which is free from mechanical failure in the case of overload.

A further object of the invention resides in the production of a recording device which may ,be regulated and operated simply and directly.

Still another object of the invention lies in the 5 production of a recording device of extreme simplicity and economy.

With these and numerous other objects in view, my invention consists in the novel features of construction, combination andfarrangement of 20 parts as will be hereinafter referred to and more particularly pointed out in the specification and claims.

In the drawing forming a part of this application:

25 Figure 1 is a central vertical longitudinal sectional view of an adaptation of the device;

Figure 2 is a transverse vertical section taken on the line 2-2 of Figure 1, looking in the direction of the arrows;

30 Figure 3 is a similar view as seen on line 3--3 of Figure 1, looking in the direction of the arrows; and

Figure 4 is a schematic diagram showing the relations of the device to associated amplification 35 apparatus.

In recording sound on film by mechanical light valve means, it is found that the mechanical inertia present in the various systems prohibits faithful recording over the entire audible range.

40 In addition, great care must be exercised in the supervision, adjustment, and control of such systems due to the extremely small physical tolerances which are allowable and due to the destructive effect of overload. The present invention 45 offers a device which is practically inertialess and which is free from the dangers of overload and the necessity for fine supervision and control.

The piezo-electric characteristics of certain crystals, as, for instance, Rochelle salt, are well 50 known. By virtue of this property electrical energy may be converted into mechanical energy, that is, electrification of such a free crystal, causes it to vibrate at a constant frequency depending on its physical and molecular dimensions.

55 The role which this phenomenon plays in monitoring the wave lengths of radio broadcast trans mitters is well known.

Consider a crystal cut in the form of a rectangular slab having its major faces perpendicular to the electric or a axis and its major 5 peripheral edges at a. forty-five degree angle to its b and "c" axes. If, now, the major faces are coated with an electrically conductive foil and alternating potential .applied thereto, the crystal will expand and contract in the direc- 10 tions of the b and c axes, provided one edge of the crystal slab is rigidly clamped. Furthermore, this extension and compression occurs in perfect synchronism with the applied potential.

The present invention utilizes such a crystal as the moving element in a light valve for phoicigraphically recording sound on motion picture m. In the accompanying drawing which is for illustrative purposes only and therefore not drawn to any particular scale, I have shown a base plate designated by the numeral l, carrying the fixedly mounted element 2 terminating in a beveled knife edge 3, adapted to coact with the knife edge 4, provided at the lower edge 4 of the pulsating crystal 5. I have also shown a chamber 6, containing an appropriate source of light I adapted to coact with a condenser 8. The numeral 9 designates the objective, and at III I have shown a strip of conventional film, on the sound groove of which the light pulsations are to be impressed. Rising from the base I is a standard I I and bolted to the upper end thereof isthe bridge member l2, carrying the manual adjusting screw l3. This manual adjusting screw [3 is adapted to enter the recess I 4 in the floating member l3a and is provided with a reduced portion l5 securely held by the screws l6. Screwed to the lower part of the member Ila, as shown at H, is a block l8 carrying a pair of clamping bolts l9, and provided at its interior with .a pocket 20 adapted to i receive a crystal 5.

In electrical relation with the faces of the crystal 5 are the electrodes 2|, and 22 denotes wires leading to the binding posts 23 from which in turn are taken off the two wires 24, leading to the amplifying means. The lower part of the member I2 is provided with laterally inwardly extending feet 25 carrying the adjusting screws 26 provided at their upper ends with cups 21 adapted to receive spiral springs 28, located within the pockets 2!. To appropriately confine the floating member l3a, the inwardly extending ledges or feet 25 are provided with upwardly extending walls 30 confining the movable element I311. It will thus be seen that I haye provided means to securely clamp one edge of the crystal and the operator has at his disposal mechanical means to accurately adjust the widths of the gap formed between the lower edge of the crystal 4 and its stationary coacting member 3.

At 3| I have shown a pair of tubes arranged in push-pull fashion and at 32 I have shown an output transformer, the primary 3! of which is ing from the spirit of the inventiomand that I do not intend any limitation to my invention except as set forth in the appended claims.

Having thus described the invention, what is claimed is:

'1. In an electro-mechanical light shuger, a fixed blade member, a piezo-electric crystal element having a blade portion complementary to and mounted to nearly touch said fixed blade member, said crystal element having two -substantially parallel faces pointing in the direction of said blade portion thereof, the end of said crystal element remote from said blade portion being fixedly mounted with reference to said fixed blade member, and a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said fixed end and said blade portion thereof.

2. In an electro-mechanical light shutter, a

-fixed blade member, a piezo-electric crystal element having a blade portion complementary to and mounted to nearly touch said fixed blade member, said crystal element having two substantially parallel faces pointing in the direction of said blade portion thereof, the end of said crystal element remote from said blade portion being fixedly mounted with reference to said fixed blade member, and a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said fixed end and said blade portion thereof, said blade portion of said crystal element being opaque to light.

3. In an electro-mechanical light shutter, a

fixed blade member, a piezo-electric crystal element having a blade portion complementary to and mounted to nearly. touch said fixed blade member, said crystal element having two substantially parallel faces pointing in the direction of said blade portion thereof, a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal 'element between the end of said crystal element remote from said blade portion thereof, and said blade portion thereof, and means for controlling the position of the end of said crystal element remote from said blade portion thereof with reference to said fixed blade member.

4. In an electro-mechanical light shutter, a fixed blade member, a substantially flat piezoelectric crystal element having flat parallel faces and having one thin end thereof mounted adjacent and complementary to and nearly touching said fixed blademember, the thin end of said crystal element opposite said end adjacent said fixed blade member being mounted in fixed position relative to said fixed blade member, and a pair of electrodes for applying potential between said fiat parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said fiat parallel faces cause corresponding variations in the length of said crystal element between said fixed end thereof and-the end thereof adjacent said fixed blade member.

5. In an electro-mechanical light shutter, a fixed blade member, a piezo-electric crystal element having two substantially parallel faces, opaque means carried by one end of said crystal element complementary to said fixed blade memberfor forming with said fixed blade member a variable light shutter, said crystal element being mounted at a point thereof removed from said .opaque means fixedly with reference. to said fixed blade member, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said fixed mounting point thereof and the end thereof carrying said opaque means, and means for applying actuating voltage to said parallel faces of said crystal element.

6. In an electro-mechanical lightshutter, a fixed blade member, a piezo-electric crystal element having two substantially parallel faces, opaque means carried by one end of said crystal element complementary to said fixed blade memher for forming with said fixed blade members variable light shutter, supporting means attached to a point of said crystal element remote from said opaque means, adjustable means for mounting said supporting means in adiustably fixed-relation to said fixed blade member, said crystal element being so cut that variations in potential applied between'said parallel faces cause corresponding variations in the length of said crystal element between said fixed mounting point thereof. and the end thereof carrying said opaque means, and means for app actuating voltage to said parallel faces of said crystal element.

7. In an electro-mechanical light shutter, a fixed blade member, a plaza-electric crystal element having a mounting portion mounted in fixed relation to said fixed-blade member and also having a complementary portion removed from said first mentioned portion and complementary to said fixed blade member for forming therewith a variable light shutter, said crystal element having two substantially parallel faces and being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said mounting portion thereof and said complementary portion thereof, and a pair of electrodes for applying potential between said parallel faces of said crystal element.

8. In an electromechanical light shutter, a piezoelectric crystal element having a terminal blade portion and two substantially parallel faces 76 pointing in the direction of said blade portion, the end of said crystal element remote from said blade portion being fixedly mounted, a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said fixed end and said blade portion thereof, and opaque means complementary to said terminal blade portion of said crystal element and adapted to form therewith a slit of variable width.

9. In an electromechanical light shutter, a piezoelectric crystal element having a terminal blade portion and two substantially parallel faces 'pointing in the direction of said blade portion, a

pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between the end of said crystal element remote from said blade portion thereof, and said blade portion thereof, opaque means complementary to' said terminal blade portion of said crystal element and adapt- .ed to form therewith a slit ofvariable width,

and means for variably controlling the position of the end of said crystal element remote from said blade portion thereof with reference to said opaque means. I

10. In the area modulation of abeam of light from a source employing a piezoelectric crystal element having two flat parallel faces and a fixed terminal portion and carrying opaque means on an opposite free terminal portion and being so cut that voltages applied across said flat faces cause corresponding variations in the length of said crystal element, the method of varying the cross-sectional area of a directly transmitted beam of light in accordance with variations in an electrical voltage which consists in variably obstructing a portion of the cross-sectional area of the path of said beam of light by variably intruding said opaque means carried by said crystal element into the path of said beam a fractional part of the breadth thereof but not entirely through said beam, and piezoelectrically instantaneously varying the portion of said cross-sectional area which is obstructed by applying said varying voltage to said opposite faces of said crystal element, whereby the unobstructed portion of said beam of light is directly transmitted from said source past said opaque means.

11. In the modulation of the intensity of a source beam of light employing a piezoelectric crystal element having two fiat parallel faces and a fixed terminal portion and carrying opaque means on an opposite free terminal portion and being so cut that voltages applied across said fiat faces cause corresponding variations in the length of said crystal element, the method of producing a concentrated light source of intensity varying in accordance with an electrical voltage which consists in directing a source beam of light upon said opaque means, variably obstructing a portion of the cross-sectional area of the path of said source beam of light by variably intruding said opaque means carried by said crystal element into the path of said source beam a fractional part of the breadth thereof but not entirely through said source beam, and thereby permitting the unobstructed portion of said source beam of light to be directly transmitted past said opaque means, optically concentrating the unobstructed portion of said source beam of light which is directly transmitted past said opaque means, and piezoelectrically instantaneously varying the portion of said cross-sectional area of said source beam which is obstructed by applying said varying voltage to said opposite faces of said crystal element.

12. In an electromechanical light shutter, a piezoelectric crystal element having a terminal blade portion and two substantially parallel faces pointing in the direction of said terminal portion, the end of said crystal element remote from said terminal portion being fixedly mounted, a first opaque means carried by said terminal portion, a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between said fixed end and said terminal portion thereof, and a second opaque means complementary to said first opaque means and adapted to form therewith a slit of variable width.

13. In an electromechanical light shutter, a piezoelectric crystal element having a terminal blade portion and two substantially parallel faces pointing in the direction of said terminal portion, a first opaque means carried by said terminal portion, a pair of electrodes for respectively applying potential between said parallel faces of said crystal element, said crystal element being so cut that variations in potential applied between said parallel faces cause corresponding variations in the length of said crystal element between the end of said crystal element remote from said terminal portion thereof carrying said first opaque means, and said terminal portion thereof, a second opaque means complementary to said first opaque means and adapted to form therewith a slit of variable width, and means for 'variably controlling the position of the end of said crystal element remote from said blade portion thereof with reference to said second opaquemeans.

STEWART C. WHITMAN. 

